Refrigeration device

ABSTRACT

A refrigeration circuit ( 1 ) sequentially connected to a compressor ( 10 ), a condenser ( 11 ), an electric expansion valve ( 13 ), an evaporator ( 17 ), and an intake proportional valve ( 21 ). When the freezing capability of the refrigeration device is to be suppressed, a control means ( 30 ) will restrict the intake proportional valve ( 21 ) in order to place refrigerant in a discharge side of the evaporator ( 17 ) in a wet saturated steam state, and the electric expansion valve ( 13 ) will be set to an aperture such that the refrigerant in the interior of the evaporator ( 17 ) will be placed in the wet saturated steam state.

TECHNICAL FIELD

The present invention relates to a refrigeration device, and moreparticularly to a refrigeration device that is capable of both freezingand chilling.

BACKGROUND ART

Refrigeration devices that are employed in containers and the like arenot only capable of freezing but are also capable of chilling, i.e.,maintaining a temperature that is slightly above the freezing point.

In this type of refrigeration device, the compressor must have asufficiently large freezing capability in order to freeze items in therefrigeration device. On the other hand, there is less demand on thecompressor during chilling than there is during freezing because thetemperature differential between the outside air and the interior of therefrigeration device is small. Thus, the compressor is stopped duringchilling, and this suppresses the capabilities of the refrigerationunit.

However, when the freezing capability of the refrigeration unit issuppressed in this manner during chilling, the compressor is frequentlystarted and stopped in order to control the temperature inside therefrigeration device, and as a result the lifespan of the compressor isshortened. In addition, there will be large changes in temperature whenit is controlled by starting and stopping the compressor, and thischaracteristic is not desirable in a refrigeration unit that is requiredto maintain a constant temperature.

Because of this, it is desirable that the compressor run as continuouslyas possible while suppressing the capability of the refrigeration unit.The following means are used to accomplish this. An intake proportionalvalve is placed on the intake side of the compressor in a refrigerationcircuit, and by closing this intake proportional valve, the amount ofrefrigerant supplied to the compressor can be suppressed. When this isdone, the amount of refrigerant in the compressor is reduced, and thusthe freezing capability of the refrigeration device is reduced. Thus,the freezing capability of the refrigeration device can be controlledwhile continuously operating the compressor.

In addition, a thermo-sensitive expansion valve is employed inconventional refrigeration devices. The thermo-sensitive expansion valvehas a thermo-sensitive line that is disposed near the outlet of theevaporator, and the temperature of the refrigerant near the outlet ofthe evaporator is slightly hotter than normal. Because of this, thetemperature near the inlet inside the evaporator will be different thenthe temperature near the outlet. This is because the thermo-sensitiveexpansion valve places the refrigerant near the outlet in thesuperheated steam state, but places the refrigerant near the inlet inthe wet saturated steam state. Thus, when a thermo-sensitive expansionvalve is used as an expansion valve, a temperature distribution will beproduced inside the evaporator.

In this situation, because the freezing capability of the refrigerationunit is being controlled during chilling, as noted above, thetemperature distribution in the evaporator is largely responsible forcreating a temperature distribution inside the refrigeration unit.Because of, this, a non-uniform temperature distribution inside therefrigeration unit will occur easily when a temperature distribution isproduced in the evaporator.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a refrigerationdevice that maintains the temperature inside the refrigeration unit at astable level when the freezing capability of the refrigeration device isbeing suppressed.

The refrigeration device according to a first aspect of the presentinvention is made of a refrigeration circuit, control means, and commandmeans. The refrigeration circuit is sequentially connected to acompressor, a condenser, an electric expansion valve, an evaporator, andan intake proportional valve. The control means controls the capacity ofthe refrigerant circuit. The command means provides commands to thecontrol means. Furthermore, when the control means receives a request tosuppress the capabilities of the refrigerant circuit from the commandmeans, the intake proportional valve will be restricted in order toplace the refrigerant in the discharge side of the evaporator in the wetsaturated steam state, and the electric expansion valve will be set toan aperture such that the refrigerant in the interior of the evaporatorwill be placed in the wet saturated steam state.

In this refrigeration device, the intake proportional valve will berestricted by the control means during chilling. When this occurs,refrigerant in the wet saturated state will be collected in the outletof the evaporator. Thus, the freezing capability of the refrigerationdevice will be suppressed and chilling will be made possible because theamount of refrigerant circulating in the refrigerant circuit will bereduced.

Furthermore, the interior of the evaporator can be filled withrefrigerant in the wet saturated state by setting the aperture of theelectric expansion valve such that the refrigerant is in the wetsaturated steam state. Refrigerant in the wet saturated state will be ata constant temperature due to the equal pressure inside the evaporator.This allows the temperature of the evaporator to be uniform both whenthe freezing capability of the refrigeration device is suppressed andwhen freezing takes place, and makes it difficult to generatetemperature irregularities. Thus, the temperature inside therefrigeration device can be maintained at a stable level.

Note that when a thermo-sensitive expansion valve is used conventionallyas an expansion valve, the temperature distribution inside theevaporator will not be uniform because the expansion valve will regulatethe refrigerant such that it will enter the superheated steam state nearthe outlet of the evaporator. However, the refrigerant in the evaporatorcan be placed in the wet saturated state and a uniform temperaturedistribution inside the evaporator can be achieved because an electricexpansion valve is employed in the present invention.

The refrigeration device according to a second aspect of the presentinvention is the refrigeration device of the first aspect, and furtherincludes a protection means that prevents damage to the compressor.

When the freezing capability of the refrigeration device is suppressedand chilling takes place, there are times when damage to the compressorwill occur. For example, when non-compressible liquid refrigerant flowstherein, it is possible to damage the compressor when it generates highpressures. Furthermore, the amount of lubricating oil inside thecompressor will be reduced, thus making it easy to bum the compressor,because the lubricating oil will be driven out of the compressor by theliquid refrigerant.

Various types of damage to the compressor can be prevented because ofthe presence of the protection means in the refrigeration device.

The refrigeration device according to a third aspect of the presentinvention is the refrigeration device of the second aspect, wherein theprotection means includes a sensor that detects the pressure andtemperature of the refrigerant in the discharge side of the compressor,and will deduce the pressure and temperature of the refrigerant in theintake of the compressor based upon the detection results from thesensor.

A sensor that detects the temperature and pressure of the refrigerant inthe discharge side of the compressor is provided as the protectionmeans. The pressure and temperature of the refrigerant in the intake ofthe compressor will be deduced from the detection results of the sensor.The pressure and temperature deduced therefrom will be used to, forexample, regulate the electric expansion valve and the intakeproportional valve, and to prevent the refrigerant in the intake of thecompressor from entering the liquid state. This will prevent damage tothe compressor.

The refrigeration device according to a fourth aspect of the presentinvention is the refrigeration device of the second aspect, in which theprotection means includes an oil temperature sensor that detects thetemperature of oil in the compressor, and will deduce the degree ofwetness of the refrigerant in the intake of the compressor based uponthe detection results from the oil temperature sensor.

Here, the degree of wetness of the refrigerant in the intake of thecompressor will be deduced from the detection results from the oilsensor serving as the protection means. The pressure and temperaturededuced therefrom will be used to, for example, regulate the electricexpansion valve and the intake proportional valve, and to prevent therefrigerant in the intake of the compressor from entering the liquidstate. This will prevent damage to the compressor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of the refrigeration device according to oneembodiment of the present invention.

FIG. 2 is a control block diagram of the refrigeration device accordingto one embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Overall Structure of the Refrigeration Device

A schematic diagram of the refrigeration device according to the presentinvention is shown in FIG. 1.

The refrigeration device according to the present invention has arefrigeration circuit 1, and as further shown in FIG. 2, is comprised ofa controller 2, an input unit 3, and an internal temperature sensor 4.

The refrigerant circuit 1 is comprised of a compressor 10, a condenser11, an electric expansion valve 13, an evaporator 17, and an intakeproportional valve 21, and are connected in sequence to each other bymeans of piping.

The compressor 10 is a device that compresses refrigerant in the vaporstate, and includes an oil temperature sensor 5 therein, and a pressuretemperature sensor 6 on the discharge side thereof. The oil temperaturesensor 5 is a device for detecting the temperature of the lubricatingoil in the compressor 10.

The condenser 11 is a device that removes heat from the refrigerant andradiates that removed heat away therefrom. The condenser 11 is connectedto the discharge side of the compressor 10 via a three way directionalcontrol valve 12.

In addition, the electric expansion valve 13 is a device that expandsthe refrigerant that passes therethrough and lowers the pressure andtemperature thereof, and is provided on the outlet side of the condenser11. Note that a receiver 14, an auxiliary heat exchanger 15, and anopen/close valve 16 are provided between the condenser 11 and theelectric expansion valve 13.

The evaporator 17 absorbs the heat from the interior of therefrigeration device and transfers the heat to the refrigerant, and isprovided on the outlet side of the electric expansion valve 13. Adistributor 18 is provided between the evaporator 17 and the electricexpansion valve 13. Note that the evaporator 17 is comprised of a mainevaporator 17 a and a sub-evaporator 17 b, with the sub-evaporator 17 bbeing provided between the electric expansion valve 13 and the condenser11.

Note also that a bypass circuit 19 is provided between the dischargeside of the compressor 10 and the evaporator 17, and a bypass valve 20is provided in the bypass circuit 19.

The intake proportional valve 21 is a device that regulates the amountof refrigerant in circulation, and is provided on the intake side of thecompressor 10.

A system block diagram of the refrigeration device is shown in FIG. 2.

The controller 2 in the refrigeration device is a microcomputer, andincludes a control means 30 and a protection means 31. The control means30 controls the refrigeration device, and the protection means 31 servesto protect against damage to the compressor 10. The control means 30 isconnected to the input unit 3 used to set the temperature inside therefrigeration unit, the internal temperature sensor 4 that detects thetemperature inside the refrigeration unit, the oil temperature sensor 5,and the pressure temperature sensor 6. In addition, the compressor 10,the electric expansion valve 13, and the intake proportional valve 21are connected to the control means 30.

Operation

The internal temperature of the refrigeration device is controlled bythe control means 30. First, the cooling of the refrigeration devicewill be described.

Freezing

The refrigeration device is a device that removes heat from the interiorthereof and radiates it to the exterior thereof by circulatingrefrigerant in the refrigerant circuit 1. The circulation of therefrigerant in the refrigerant circuit 1 will be described below.

First, the refrigerant absorbs the heat inside the refrigeration deviceby means of the evaporator 17. The refrigerant that has absorbed thisheat is sent to the compressor 10 via the intake proportional valve 21.The refrigerant is compressed into a high temperature high pressure gasin the compressor 10, and sent to the evaporator 11. The heat in therefrigerant is radiated to the exterior of the refrigeration device inthe evaporator 11, thereby lowering the temperature thereof. Thus, theheat that was absorbed by the refrigerant in the evaporator 17 will beremoved by the condenser 11. In addition, the refrigerant is sent fromthe condenser 11 to the electric expansion valve 13 and expanded, andthen returned to the evaporator 17.

The control means 30 controls both the amount of refrigerant incirculation in the refrigerant circuit 1 and the temperature inside therefrigeration device by controlling the compressor 10, the electricexpansion valve 13 and the intake proportional valve 21. Duringfreezing, there is a large amount of refrigerant in circulation, and theheat inside the refrigeration device is removed to the exterior thereofin accordance with the temperature set in the input unit 3.

Chilling

On the other hand, during chilling the freezing capability of therefrigeration device is suppressed in order to bring the temperatureinside the refrigeration unit to a point just above the freezing point.The means of suppressing the freezing capability will be describedbelow.

In order to suppress the freezing capability, the intake proportionalvalve 21 will first be restricted. Thus, the refrigerant in the line upto the intake proportional valve 21 can be collected in the wetsaturated state, and the amount of refrigerant circulating in therefrigerant circuit 1 can be controlled. In addition, in this state eventhe refrigerant in the outlet of the evaporator 17 can be placed in thewet saturated state by opening and regulating the electric expansionvalve 13. Thus, the amount of refrigerant in circulation in therefrigerant circuit 1 can be reduced to a suitable level because therefrigerant in the line from the outlet of the evaporator 17 to theintake proportional valve 21 can be collected in the wet saturatedstate. Because of this, the freezing capability of the refrigerationdevice can be suppressed, and thus it can be operated in the chillingmode.

In addition, the refrigerant in the wet saturated state inside theevaporator 17 can be collected by further opening the electric expansionvalve 13. At this point, the temperature of the refrigerant in the wetsaturated state collected in the evaporator 17 will be constant becausethe pressure of the refrigerant inside the evaporator 17 is constant.Because the temperature of the refrigerant is constant, the heatabsorbed from the interior of the refrigeration device in the evaporator17 will be uniform. Thus, temperature irregularities inside therefrigeration unit can be suppressed.

Protection of the Compressor During Chilling

The refrigerant in the intake of the compressor is in the superheatedsteam state during freezing.

However, when suppressing the freezing capability and conductingchilling in the refrigeration device, the refrigerant in the intake ofthe compressor will be in the wet saturated state. Refrigerant in thewet saturated state includes refrigerant in the liquid state. Becauseliquids are different from gases and cannot be compressed, there is arisk that a pressure will be generated inside the compressor 10 that ishigher than the maximum allowed, and thus creating damage therein, whenthere is a large amount of refrigerant in the liquid state in thecompressor 10 during operation. Furthermore, there are times whenrefrigerant in the liquid state will force out the lubricating oil inthe compressor 10 to the exterior thereof. If this occurs, the amount oflubricating oil in the compressor 10 will be reduced, thus creating thepossibility that the compressor 10 will be burned.

Thus, the electric expansion valve 13 and the intake proportional valve21 must be controlled by the control means 30 in order to place therefrigerant in the intake of the compressor 10 in the superheated steamstate. Therefore, it is necessary to know the state of the refrigerantin the intake of the compressor 10, but this can be determined from thepressure and temperature of the refrigerant.

However, because there is little refrigerant in circulation, thepressure of the refrigerant in the inlet of the compressor 10 will beextremely low, a normal pressure sensor will give an inaccurate reading,and thus the current state of the refrigerant will be unclear.

Thus, the protection means 31 will deduce the pressure and temperaturein the intake of the compressor 10 based upon the detection results fromthe oil temperature sensor 5 and the pressure temperature sensor 6. Thesuperheated temperature of the refrigerant in the discharge side of thecompressor 10 can be clearly determined by the pressure temperaturesensor 6. The degree of wetness of the refrigerant in the intake of thecompressor 10 can be determined by the degree that the refrigerant issuperheated. Furthermore, because the degree of wetness of therefrigerant can be deduced by means of the results from the oiltemperature sensor 5, it is possible to make a more accuratedetermination. Thus, the control means 30 can be used to control thefreezing capability of the refrigeration device such that damage to thecompressor 10 is avoided.

INDUSTRIAL APPLICABILITY

In the refrigeration device according to the first aspect, thetemperature of the evaporator will be uniform when the freezingcapability of the refrigeration device is suppressed and when freezingoccurs, and temperature irregularities will be difficult to produce.

In the refrigeration device according to the second aspect, varioustypes of damage to the refrigeration device can be avoided because ofthe presence of the protection means.

In the refrigeration device according to the third aspect, therefrigerant in the intake of the compressor can be prevented fromentering the liquid state by the protection means because the pressureand the temperature of the refrigerant in the intake of the compressorwill be deduced from the detection results of the sensors.

In the refrigeration device according to the fourth aspect, therefrigerant in the intake of the compressor can be prevented fromentering the liquid state by the protection means because the degree ofwetness of the refrigerant in the intake of the compressor will bededuced from the detection results of the oil temperature sensor.

What is claimed is:
 1. A refrigeration device, comprising: arefrigeration circuit being sequentially connected to a compressor, acondenser, an electric expansion valve, an evaporator, and an intakeproportional valve; a control means for controlling the capacity of saidrefrigerant circuit; and a command means for providing indicators tosaid control means; said control means being configured to receive arequest to control said capacity of said refrigerant circuit from saidcommand means, said intake proportional valve being configured to berestricted to place refrigerant in a discharge side of said evaporatorin a wet saturated steam state, and said electric expansion valve beingconfigured to be set to an aperture to place refrigerant in an interiorof said evaporator in said wet saturated steam state.
 2. Therefrigeration device set forth in claim 1, further comprising aprotection means for preventing damage to the compressor.
 3. Therefrigeration device set forth in claim 2, wherein said protection meansincludes a sensor that detects a pressure and temperature of refrigerantin a discharge side of said compressor, and to deduce a pressure andtemperature of refrigerant in an intake of compressor based upon thedetection results from said sensor.
 4. The refrigeration device setforth in claim 2, wherein said protection means includes an oiltemperature sensor that detects a temperature of oil in said compressor,and to deduce a degree of wetness of refrigerant in an intake of saidcompressor based upon detection results from said oil temperaturesensor.
 5. The refrigeration device set forth in claim 1, wherein saidinterior of said evaporator is configured to be filled with saidrefrigerant in said wet saturated state by setting said aperture of saidelectric expansion valve such that said refrigerant is in said wetsaturated steam state.